Modern automobile body shapes are distinguished by relatively large window areas. Because of strong sunlight, the large window areas result in considerable heat generation in the interior of the vehicle and, in connection with vehicles with air conditioning, this extensive heat generation results in a not inconsiderable use of energy in order to counteract the heating effects on the vehicle.
For this reason, motor vehicles are increasingly equipped with windup window shades.
In this connection it is known to attach two guide rails laterally next to the window, in which the end of the traction rod of the window shade web is guided. The length of the traction rod is adjustable in order to be able to accommodate various window widths. Actuation takes place by means of the thrust members running in the guide rails.
The thrust members can only be sufficiently adjusted with a very large outlay, so that they move the traction rod of the window shade web exactly parallel to the windup shade. If there is a lack of parallelism, the window shade web is pulled obliquely, which results in waves extending obliquely in the extended window shade web. This does not look nice and is objected to.
Based on the foregoing it is the object of the invention to create a windup window shade for motor vehicles, wherein inexactly adjusted thrust members cannot cause warping of the window shade web.
In accordance with the invention, this object is attained by a windup window shade for regulating the entry of light through a window into the interior of a motor vehicle, in particular a rear window windup shade, having: at least one windup shaft that is rotatably seated; at least one window shade web that is fastened along one edge to the windup shaft, whose edge that is parallel with the one edge is connected with an associated traction rod, and which has lateral longitudinal edges, wherein, in the course of the extension of the window shade web, the traction rod has a nominal position with respect to the windup shaft which position is a function of the position of the window shade web, and in which no transverse tensions occur; at least one pair of guide means, each of which extends laterally beside the extended window shade web, and each of which contains at least a guide groove in which the ends of the traction rod are guided; a drive mechanism, which has first and second drive or thrust members that are arranged such that an effective end of the first drive member acts together with or on the one end of the traction rod, and the effective end of the second drive member acts together with or on the other end of the traction rod, and, a compensating device that at least reduces a displacement of the traction rod by the thrust or drive members out of the nominal position.
The displacement out of the nominal position essentially occurs because the drive members used for moving the traction rod have a distance from the windup shaft which is different from the nominally required effective distance. Another cause of skewed pulling of the window shade web is due to a traction rod which from the start does not extend in accordance with the nominal position and acts together with exactly adjusted drive members.
If, for example, the drive members operate as thrust members and are moved synchronously by an electric motor in the sense of taking the traction rod along for pulling the window shade web out, an uneven tension is created in the window shade web with the result of a wave formation, if the one thrust member precedes and thereby displaces the traction rod out of its natural position which, in case of a rear window, extends parallel with the window shade web, for example.
The problems inherent in the displacement of the traction rod and in adjustment are increased because the drive members act together interlockingly with the gear motor. Because of this, an offset up to almost one tooth spacing can occur between the two drive members, which in actual use amounts to approximately between 3 and 6 mm. Added to this is the tolerance with which the window shade web is produced. The traction rod can inherently show a parallelism error in relation to the windup shaft because of sewing and cutting tolerances.
If these tolerances overlap in a disadvantageous manner, errors of up to 10 mm and more are not impossible. Such an effective offset results in an oblique stress on the window shade web with the result of obliquely extending waves or folds in the window shade web.
Similar conditions also basically arise in connection with side windows. However, here the traction rod is in an oblique position in relation to the windup shaft anyway, i.e. in the nominal position the traction rod extends obliquely in respect to the windup shaft. If in this case the traction members act in an offset manner and forcibly change the natural position of the traction rod, wave formation will also result.
The compensating device in accordance with the invention automatically ensures that the displacement of the traction rod out of the respective nominal position (obliquely or parallel) occurs at least to a lesser extent and that no visible wave formation in the window shade web is caused.
Several basic solutions regarding the compensating device are possible in principle.
In accordance with one solution, the windup shaft of the window shade web is seated in a hoop, which itself can swing in a limited way around the transverse axis.
The axis is preferably located in the center in relation to the longitudinal extension of the windup shaft. Because of this, the windup shaft can adjust itself in such a way that the traction rod maintains the nominal position in relation to the windup shaft.
Instead of seating the windup shaft in a hoop, it is possible to achieve the same goal if the one end of the windup shaft is seated in a stationary bearing, which is limitedly pivotable, or makes an appropriate tilting play available for the windup shaft, while the windup shaft can move freely to a large extent in the other bearing in respect to a plane, which is parallel with the plane defined by the extended window shade web.
For compensating tolerance errors in both directions, the windup shaft has of course an opposite inclination in the position of rest.
The bearing, which is simultaneously used as the anchoring of the spring drive, is preferably stationary. In this case it is sufficient if an oblong hole is provided for the other bearing bore, in which a bearing journal is displaceably seated.
Finally, a further actual option for locating the compensating device consists in the arrangement of spring members between the drive members and the traction rod. Because of their resilience, the spring members reduce the force difference occurring at both ends of the traction rod and leading to wave formation.
The guide means of the window shade web of the invention preferably consist of guide rails in which guide grooves are contained.
The guide groves can be simultaneously used for guiding the thrust members secure from kinking.
The drive mechanism becomes particularly simple if the windup shaft is biased in the windup direction of the window shade web with the aid of a spring drive. In this case the windup shaft is forced to follow the movement of the window shade web as impressed on the traction rod by the electric motor and the drive members.
The window shade web can consist of a woven material or a perforated or dyed foil.
In connection with windows whose surfaces differ from the rectangular shape, the traction rod is length-adjustable in order to be able to follow the changing distance between the guide rails.
Further embodiments of the invention are inter alia subject of dependent claims. It is intended here that also those combinations of characteristics are considered to be claimed, for which there is no explicit exemplary embodiments.